Isothermal torrefaction of coconut fiber in a fixed bed reactor

Abstract

Torrefaction of coconut fiber was performed in a fixed bed reactor at torrefaction temperature of 220-300°C and holding time of 20-60 mins under nitrogen atmosphere. The torrefaction reaction kinetics were determined using the Coats-Redfern method. The values of activation energy and pre-exponential factor at holding time of 20, 40 and 60 minutes are in the range of 30.25-43.61 kJ/mol and 4.03-152.69 min -1 respectively. The proximate analysis was performed on the raw and torrefied coconut fiber. It was identified that the moisture content and volatile matter decreased but the ash content and the fixed carbon increased when the torrefaction temperature were increased from 220-300 °C. The morphological properties of coconut fiber and torrefied coconut fiber were analyzed using Scanning electron microscope (SEM). From SEM, the degree of severity due to torrefaction process towards the surface structure of torrefied coconut fiber can be visualized and increased with increasing torrefaction temperature with merging of pores. The existence of functional group such as hydroxyl (O-H) and alkane (C-H) were identified on the surface of raw and torrefied coconut fiber by Fourier Transform Infrared spectroscopy (FTIR).